Pruritus, or pruritis, the unpleasant cutaneous sensation/itchiness that evokes a reflex behavior involving scratching directed at the skin, represents a significant clinical problem that has a very diverse etiology. Chronic pruritus can be manifested in 8-12% of the human population. Because of its clinical significance, mechanisms of pruriception are an important research topic. An important issue in advancing pruritus research is the development of a reliable and easily implemented method to assess hind paw scratching in animal, e.g., rodent, experimental models after exposure to a pruritic agent.
There are published strategies to assess rodent scratching. The most widely used strategy is manual counting through visual observation by a trained observer in real time or via recorded media. However, this process is subject to inter-observer bias and observer fatigue. Several automated systems have also been described. One such system involves processing videotaped behavior using motion detection software. This process requires specialized camera equipment and computer-intensive motion detection software. Another system involves the assessment of acoustic waveforms produced by paw movement. This system depends on eliminating external noise, and results in a lack of ability to determine the specific origin of the movement which evokes the sound. Yet another system involves assessing whole body movement using a strain gauge mounted cage. This system measures whole body activity, but not specifically homolateral paw movement. Still another system detects paw movement with a subcutaneous magnet, posing the need to implant a foreign body into a subject. Further still, detection, by a magnetic field, of movement of a ring attached to the lower leg (around the tibia just above the ankle) is also suggested, but can lead to limb swelling.
As seen from the aforementioned description, conventional systems for assessing itching employ labor-intensive visual counting either in real time or by media recording. While automated systems do exist, such systems proposed thus far are either extremely computer intensive (e.g., by requiring video analysis), non-selective (e.g., reliant upon body movement), invasive technologies (e.g., implanting subcutaneous magnets) and/or involve restrictive bands potentially impeding blood flow or causing localized inflammation (e.g., using constrictive bands).